Sessions and MD5

Hey Guys, I am looking for a quick way to do form validation using $_SESSION variables and MD5, but my brain is mush and my logic is all botched. Heres the scoop... I am using 3 $_SESSION variables to test for MD5. 1. $_SESSION["MD5_OLD"] 2. $_SESSION["MD5_NEW"] 3. $_SESSION["MD5_VALID"] $_SESSION["MD5_NEW"] is rebuilt with each form submission based on 3 other $_SESSION variables. Code block follows.... // If NOT set set to zero if (!(isset($_SESSION["MD5_NEW"]))) { $_SESSION["MD5_NEW"] = 0; } // If NOT set set to zero if (!(isset($_SESSION["MD5_OLD"]))) { $_SESSION["MD5_OLD"] = 0; } // If NOT set set to zero if (!(isset($_SESSION["MD5_VALID"]))) { $_SESSION["MD5_VALID"] = 0; } // If var3 is set, build MD5_NEW if (isset($_SESSION["var3"])) { $_SESSION["MD5_NEW"] = $_SESSION["var1"].$_SESSION["var2"].$_SESSION["var3"]; } if ( md5($_SESSION["MD5_NEW"]) == md5($_SESSION["MD5_OLD"])) { echo "No Changes to MD5"; } else { echo "MD5 has CHANGED!<BR>"; $_SESSION["MD5_NEW"] = $_SESSION["MD5_VALID"]; } $_SESSION["MD5_OLD"] = $_SESSION["MD5_VALID"]; // End Code block Ok, so where is the err in my logic since I know there is one, because after var3 is set I keep getting "MD5 has changed", or I just don't understand the proper use of MD5, most likely both :) Thanks Chris